import java.util.Map;
import org.jspecify.annotations.Nullable;

/** A {@code RegularImmutableTable} optimized for dense data. */
@GwtCompatible
@Immutable(containerOf = {"R", "C", "V"})
final class DenseImmutableTable<R, C, V> extends RegularImmutableTable<R, C, V> {
  private final ImmutableMap<R, Integer> rowKeyToIndex;
  private final ImmutableMap<C, Integer> columnKeyToIndex;
  private final ImmutableMap<R, ImmutableMap<C, V>> rowMap;

  private static final SparseImmutableTable<Character, Integer, String> SPARSE =
      new SparseImmutableTable<>(CELLS.asList(), ROW_SPACE, COLUMN_SPACE);

  private static final DenseImmutableTable<Character, Integer, String> DENSE =
      new DenseImmutableTable<>(CELLS.asList(), ROW_SPACE, COLUMN_SPACE);

  @Override
  Iterable<ImmutableTable<Character, Integer, String>> getTestInstances() {

    // TODO(gak): tune this condition based on empirical evidence
    return (cellList.size() > (((long) rowSpace.size() * columnSpace.size()) / 2))
        ? new DenseImmutableTable<R, C, V>(cellList, rowSpace, columnSpace)
        : new SparseImmutableTable<R, C, V>(cellList, rowSpace, columnSpace);
  }

  /**
   * @throws IllegalArgumentException if {@code existingValue} is not null.